U.S. patent number 4,523,468 [Application Number 06/538,627] was granted by the patent office on 1985-06-18 for phased array inspection of cylindrical objects.
This patent grant is currently assigned to TRW Inc.. Invention is credited to Thomas Derkacs, Istvan M. Matay, Stephan D. Murphy, John Touhalisky.
United States Patent |
4,523,468 |
Derkacs , et al. |
June 18, 1985 |
Phased array inspection of cylindrical objects
Abstract
A first array (A) of ultrasonic transducers transmits ultrasonic
shear waves circumferentially around an examined cylindrical object
(110). A second array (B) transmits ultrasonic shear waves axially
along the examined object. Triggering pulses from a triggering
amplifier (22) are switched by a multiplexer (24) to each
individual transducer of the first and second arrays. As one of the
transducers assumes the role of a transmitting transducer and
transmits an ultrasonic wave, the other transducers of the first
and second arrays assume a receiving mode to receive reflected
ultrasonic components. A wave travel timer (26) measures the
duration for an ultrasonic wave to be transmitted from the
transmitting transducer to a defect and for a reflected component
to propagate from the defect to the receiving transducer. A
microprocessor (20) tri-angulates or otherwise computes the
location and orientation of a reflective defect from the measured
travel time, the spatial relationship of the transmitting and
receiving transducers, and the direction of propagation of the
transmitted ultrasonic wave.
Inventors: |
Derkacs; Thomas (Mayfield
Village, OH), Matay; Istvan M. (North Royalton, OH),
Murphy; Stephan D. (East Cleveland, OH), Touhalisky;
John (Eastlake, OH) |
Assignee: |
TRW Inc. (Cleveland,
OH)
|
Family
ID: |
24147717 |
Appl.
No.: |
06/538,627 |
Filed: |
October 3, 1983 |
Current U.S.
Class: |
73/598; 73/622;
73/626; 73/628 |
Current CPC
Class: |
G01N
29/07 (20130101); G01N 29/262 (20130101); G01N
2291/2634 (20130101); G01N 2291/044 (20130101); G01N
2291/106 (20130101); G01N 2291/02854 (20130101) |
Current International
Class: |
G01N
29/26 (20060101); G01N 29/04 (20060101); G01N
29/07 (20060101); G01N 029/04 () |
Field of
Search: |
;73/597,598,600,620,622,625,626,628,637,638,640,641 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
H Seiger, "Comparison of Three Flaw-Location Methods for Automated
Ultrasonic Testing", NDT International, pp. 131-135, Jun.
1982..
|
Primary Examiner: Kreitman; Stephen A.
Attorney, Agent or Firm: Blackhurst; Daniel G.
Claims
Having thus described the invention, it is now claimed:
1. A method of ultrasonically locating defects in an examined
object with a first transducer array including a plurality of
transducers for generating ultrasonic shear waves along the
examined object in a first transmission direction and for receiving
reflected ultrasonic wave components from the examined object and a
second transducer array for transmitting ultrasonic shear waves
along the examined object in a second transmission direction and
receiving reflected ultrasonic wave components from the examined
object, the method comprising:
(a) actuating at least one transducer of the first and second
arrays to transmit an ultrasonic shear wave along the examined
object and causing the remaining transducers of the first and
second arrays to assume a reflected component receiving mode;
(b) measuring an ultrasonic wave travel time between transmission
of an ultrasonic wave by a transmitting transducer and receipt of a
reflected component by a receiving transducer;
(c) determining the spatial relationship between the transmitting
transducer and the receiving transducer;
(d) determining the location of the defect flaw from the measured
travel time and the relative spatial relationship of the
transmitting and receiving transducers; and,
(e) repeating steps (a)-(d) with other transducers of the first and
second arrays.
2. The method as set forth in claim 1 further including the step of
determining the angular orientation of the defect relative to the
transmission direction of each transmitted ultrasonic wave.
3. The method as set forth in claim 1 further including measuring
the amplitude of the reflected component relative to the amplitude
of the transmitted ultrasonic wave.
4. The method as set forth in claim 1 wherein a single transducer
is actuated at a time to function as the transmitting
transducer.
5. The method as set forth in claim 1 wherein the examined object
is generally cylindrical, the first transmission direction being
circumferentially of said object and the second transmission
direction being axially along said object.
6. The method as set forth in claim 1 wherein the step of
determining the location of the defect includes determining the
shear wave velocity of ultrasonic shear waves in traversing the
examined object.
7. The method as set forth in claim 6 wherein the step of
determining the defect location further includes multiplying the
measured travel time by the determined shear wave velocity to
determine the distance which the ultrasonic wave traveled from the
transmitting transducer to the defect and to the receiving
transducer.
8. The method as set forth in claim 7 wherein the defect location
determining step further includes (1) determining the relative
position between the first and second arrays and a preselected
origin on the examined object, (2) determining the spatial
relationship of each transmitting transducer and the first and
second arrays, and (3) determining a position of the defect
relative to the preselected origin.
9. An ultrasonic inspection apparatus for locating defects in an
examined object, the apparatus comprising:
a first transducer array including a plurality of first ultrasonic
transducers, each first ultrasonic transducer transmitting in
response to a trigger signal an ultrasonic shear wave which travels
in a first direction along the examined object and producing an
echo signal in response to receiving a reflected ultrasonic
component;
a second transducer array including a plurality of second
ultrasonic transducers, each second ultrasonic transducer
transmitting in response to a trigger signal an ultrasonic shear
wave which travels in a second direction along the examined object
and producing an echo signal in response to receiving a reflected
ultrasonic component;
multiplexer means for selectively switching trigger pulses to
preselected transmitting transducers of the first and second
arrays;
travel time measuring means for measuring time between transmission
of an ultrasonic wave by the transmitting transducer and receipt of
a reflected component by a receiving transducer, the travel time
measuring means being operatively connected with the first and
second ultrasonic transducer arrays;
location determining means operatively connected with the travel
time measuring means and the first and second ultrasonic transducer
arrays for determining the location of a reflective defect from the
measured travel time and the spatial relationship of the
transmitting and receiving transducers.
10. The inspection apparatus as set forth in claim 9 further
including defect orientation determining means for determining an
angular orientation of a defect surface from the determined defect
location and the spatial relationship of the transmitting and
receiving ultrasonic transducers.
11. The inspection apparatus as set forth in claim 9 further
including reflected component amplitude measuring means for
measuring the amplitude of the received reflected component.
12. The inspection apparatus as set forth in claim 9 wherein the
first direction is substantially perpendicular to the second
direction.
13. The inspection apparatus as set forth in claim 12 wherein the
examined object is generally cylindrical with the first direction
being circumferentially around the object and the second direction
being axially along the object.
14. The inspection apparatus as set forth in claim 9 wherein the
location determining means includes shear wave velocity determining
means for determining the velocity of ultrasonic shear waves
traversing the examined object.
15. The inspection apparatus as set forth in claim 14 wherein the
location determining means includes multiplying means for
multiplying the measured travel time by the determined shear wave
velocity to determine the distance which the ultrasonic wave
traveled from the transmitting transducer to a defect and to the
receiving transducer.
16. The inspection apparatus as set forth in claim 15 wherein the
location determining means includes relative location means for
determining the location of the defect relative to the transmitting
transducer and origin means for adjusting the relative location for
the spatial relationship of the transmitting transducer relative to
a preselected point of origin on the examined object.
Description
BACKGROUND OF THE INVENTION
The present invention relates to the art of acoustical defect
detection. The present invention finds particular application in
the ultrasonic inspection of cylindrical objects such as metal pipe
and tubing, and will be described with particular reference
thereto. It is to be appreciated, however, that the invention has
other applications including acoustical examination of sheet
materials, polygonal members, rods, and the like.
Heretofore, ultrasonic transducers have been utilized in a
pulse-echo mode to locate flaws and defects in an examined object.
In the pulse-echo mode, an ultrasonic transducer is first caused to
transmit an ultrasonic wave and then waits to receive an echo from
a defect. The angle of incidence and angle of reflection relative
to the surface of the defect must be equal. Thus, a transmitting
transducer can only receive an echo from a defect surface which is
substantially normal to the direction of ultrasonic wave
transmission. Defect surfaces which are more than 5.degree.
off-normal to the direction of propagation reflect the ultrasonic
wave, but do not return a sufficiently large component to the
transmitting transducer for the defect to be detected.
Ultrasonic transducers have been used in a pulse-echo mode to
generate ultrasonic shear waves traveling peripherally around the
examined object, and to detect echoes reflected peripherally back
to the transducer. Axially oriented ultrasonic transducers have
been used to generate axial shear waves and detect axial echoes.
Similarly, ultrasonic transducers have been oriented perpendicular
to the examined surface and operated in a pulse-echo mode. Further,
others have oscillated or rocked the transducers to examine the
object from a multiplicity of angles.
A three dimensional defect commonly has at least some surface
portion which is normal to one of the pulse-echo operated
transducers and is readily detected. However, a two dimensional
defect, such as a crack, can only be detected by pulse-echo
transducers which are oriented substantially perpendicular to the
surface of the crack. Thus, peripherally oriented pulse-echo
transducers and axially oriented pulse-echo transducers are only
able to detect cracks which are substantially parallel or
perpendicular to the axis.
It has been suggested to have ultrasonic transducers propagate
ultrasonic waves around the examined object in a spiral at various
angles, eg., 45.degree.. However, because the direction of
propagation must be within 5.degree. of normal to a crack to be
assured of detection, a wide range of wave propagation directions
would be required for assuring that cracks would not go
undetected.
The present invention contemplates an arrangement which overcomes
the above referenced problems and others, and provides an
ultrasonic inspection system which detects defects and cracks
oriented at a wide variety of orientations in an examined
object.
SUMMARY OF THE INVENTION
In accordance with the present invention, there is provided a
method of ultrasonically locating defects in an examined object
with first and second transducer arrays. The first transducer array
is disposed for transmitting and receiving ultrasonic waves
propagating in a first direction, and the second array disposed for
transmitting and receiving ultrasonic waves propagating in a second
direction. The transducers in the first transducer array are
actuated individually or in small groups to transmit an ultrasonic
wave. The transducers in both arrays are operated in a receive mode
to receive ultrasonic echoes. The travel time between transmission
of the wave and receipt of an echo is measured. From the wave
transmission direction, travel time, and the spatial relationship
of the transmitting and receiving transducers, the location of a
reflective defect is tri-angulated or otherwise determined. This
process is repeated with each transducer in the first and second
arrays operated in its transmission mode.
In accordance with another aspect of the invention, an ultrasonic
defect detection apparatus is provided. A first transducer array,
including a plurality of first transducers, is disposed for
transmitting ultrasonic shear waves along the examined object in a
first direction. A second transducer array including a plurality of
second transducers is disposed to transmit ultrasonic shear waves
along the object in a second direction. A multiplexing means
selectively switches triggering pulses to each transducer of the
first and second ultrasonic transducer arrays. After each
transmission, the first and second ultrasonic transducer arrays
assume a receiving mode. An ultrasonic wave travel time measuring
means measures the time between transmission of the ultrasonic wave
and receipt of an echo. A defect location determining means
determines the location of a reflective defect from the wave
transmission direction, the determined travel time, and the spatial
relationship of the transmitting and receiving transducers.
A primary advantage of the present invention is the detection of
two dimensional defects and cracks having substantially any
orientation.
Another advantage of the invention resides in the capability to
examine an object for defects relatively quickly and
accurately.
Still another advantage of the invention is found in the accurate
location and determination of defect dimensions.
Still other advantages and benefits of the present invention will
become apparent to those of ordinary skill in the art upon reading
and understanding the following detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention may take form in various steps and arrangements of
steps and in various parts and arrangements of parts, preferred and
alternative embodiments of which will be described in detail in the
following specification and illustrated in the accompanying
drawings which form a part hereof and wherein:
FIG. 1 is a diagrammatic illustration of a microprocessor based
apparatus for detecting defects in accordance with the present
invention;
FIGS. 2A, 2B, and 2C illustrate exemplary pulse-echo reflection
modes in accordance with the present invention; and
FIG. 3 is a diagrammatic illustration of an alternative defect
detecting apparatus in accordance with the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
With reference to the drawings wherein the showings are for
purposes of illustrating preferred and alternative embodiments of
the invention only and not for purposes of limiting same, each
transducer of a first transducer array A in FIG. 1 is oriented so
as to transmit ultrasonic waves propagating along an examined
object in a first direction. Each transducer of a second transducer
array B is oriented to generate ultrasonic waves propagating in a
second direction.
In the preferred embodiment, the first and second directions are
orthogonal to the circumferential direction. The use of orthogonal
propagation directions simplifies the algorithm for determining the
position at which a flaw is located, but is not required. An
electronic circuit C selectively actuates or triggers transducers
of the first and second arrays to generate ultrasonic waves
propagating in the first and second directions, causes the
transducers of the first and second arrays to assume an echo
receiving mode, and determines the size, location, orientation, and
other physical characteristics of cracks and defects.
In the preferred embodiment, the examined object comprises a
cylindrical steel pipe or tube 10. The transducers of the first
ultrasonic array A are disposed to propagate ultrasonic waves
through a coupling medium in a collar 12 to the examined object.
The transducers of the first array are oriented such that shear
waves are propagated circumferentially around the examined object.
The transducers of the second array are oriented to transmit
ultrasonic waves through the coupling medium to propagate
ultrasonic shear waves axially along the examined object. In the
preferred embodiment, the first and second transducer arrays are
disposed circumferentially or peripherally around the entirety of
the object. Alternately, the first and second arrays may extend
only partially around the examined object, and the examined object
may be rotated to bring all portions thereof into association with
the transducer arrays. As the object 10 is relatively moved axially
through the first and second arrays, A, B, a position encoder 14
produces electronic signals indicative of the location of the
arrays relative to an arbitrary point or origin of the object.
A microprocessor 20 periodically enables or actuates a triggering
means 22 causing it to produce an ultrasonic transducer trigger
pulse. A multiplexing means 24 switches the triggering pulse to a
selected ultrasonic transducer of the first and second arrays. The
microprocessor controls the multiplexing means such that the
multiplexing means selectively switches trigger pulses serially to
each of the transducers in the first and second arrays. An
ultrasonic wave travel timer 26 measures the time interval between
transmission of an ultrasonic wave and receipt of an ultrasonic
echo. Although illustrated as a separate component connected with
the triggering means and with the transducers of the first and
second arrays, the wave travel timing means may comprise an
integral part of the microprocessor 20. Optionally, one or more
transducers 28 may be disposed a preselected distance from one of
the axial transducers to measure the velocity of the ultrasonic
shear waves in the examined object.
The microprocessor is programmed to calculate the location of each
defect which produces a received ultrasonic echo and display the
defect location on a display means 30. In this manner, the
microprocessor functions as a location determining means which
determines defect locations from the spatial relationship of the
transmitting and receiving transducers, the direction of
transmission of the ultrasonic wave, and the travel time. In
addition, the microprocessor determines and displays other
characteristics of each defect, such as the orientation of the
reflecting surface, the reflectivity of the defect, and the
like.
The location of the flaws is calculated using a form of
triangulation. It is to be appreciated that the transmitting
transducer, the defect, and the receiving transducer define the
three corners of a triangle. The spatial relationship of the
transducers determines the length of one side of the triangle, ie.,
the distance between the transmitting and receiving transducers.
The direction of propagation determines the angle between the sides
of the triangle which meet at the transmitting transducer. The wave
travel time in conjunction with a premeasured propagation speed
provides an indication of the sum of the length of the other two
sides of the triangle. From this data, the location and angular
orientation of a defect relative to the transmitting transducer may
be calculated.
With reference to FIG. 2A, one or another preselected number of the
transducers in the first and second arrays A, B is triggered to
generate an ultrasonic shear wave. As illustrated, one of the axial
transducers 40 generates an ultrasonic shear wave 42 propagating
axially along the examined object. Upon encountering a crack 44 or
other defect, the ultrasonic wave is reflected or echoes and
produces a reflected component 46. The transmitting ultrasonic
shear wave 42 strikes the crack 44 at a point of intersection 48 at
an angle 50, known as the angle of incidence. The reflected
component 46 is reflected from the crack at an angle 52, known as
the angle of reflection.
The angle of incidence and the angle of reflection are measured
relative to a tangent to the point of intersection. In such an
interaction, the angle of reflection is equal to the angle of
incidence. Thus, the angular orientation of the crack 44 determines
the direction in which the reflected component propagates. The
reflected component intersects another of the transducers, eg., a
transducer 54 of the second array B in the illustration of FIG. 2A.
From this information, the point at which the ultrasonic wave
struck the crack and the angular orientation of the crack relative
to the axial direction are readily determined.
Specifically, it is to be appreciated that a right triangle is
defined between the generating transducer 40, the point of
intersection 48 with the crack, and the receiving transducer 54.
The travel time between transmission of the ultrasonic wave and
receipt of the echo component is readily measurable. Further, the
velocity of the shear wave is readily determinable by experimental
measurement or the like.
These experimental relationships can be described mathematically as
follows:
where d.sub.42 is the distance between the transmitting transducer
and the crack, d.sub.46 is the distance between the crack and the
receiving transducer, V.sub.s is the velocity of the shear wave, t
is the elapsed time between transmission and receipt, and d.sub.t
is the distance between the transmitting and receiving transducers.
These equations are readily solvable in terms of the distance in
the axial direction between the transmitting transducer 40 and the
crack: ##EQU1##
Similarly, the equal angles of incidence reflection are readily
determinable from the quadratic equations:
where .theta. is the angle between the surface normal and each of
ultrasonic wave 42 and reflected component 46, and .phi. is each of
the equal angles between the surface tangent and each of the
ultrasonic wave 42 and the reflected component 46. These equations
are readily solvable for the angle .phi. between the defect surface
and the direction of propagation and the angle .theta. between the
surface normal and the direction of propagation: ##EQU2## Further,
from the intensity of the reflected component, ie., the relative
magnitude of the transmitted wave 42 and the reflected component
46, the reflectivity and other physical properties of the defect
are determinable.
In FIG. 2B, like components to the components of FIG. 2A are
identified by the like reference numerals with a primed (') suffix.
A transmitting transducer 40' transmits an ultrasonic wave 42'
which interacts with a defect 44'. The orientation of the defect
surface is such that a reflected component 46' is produced. In the
situation of FIG. 2B, the reflected component propagates in a
circumferential direction and is received by a receiving transducer
54'. Analogously, the distance in the axial direction from the
transmitting transducer to the defect, and the angle of the defect
surface relative to the axial direction may both be calculated from
the spatial relationship of the transmitting and receiving
transducers, the direction of wave propagation, and the wave travel
time.
In the showings of FIG. 2C, like components to the components of
FIGS. 2A and 2B are identified by like numerals with a double
primed (") suffix. A transmitting transducer 40" of the
circumferential array A generates a circumferential ultrasonc wave
42" which interacts with a crack 44". A reflected component 46"
reflects from the crack such that an angle of incidence 56" equals
an angle of reflection 52". This echo direction results in a
receiving transducer 54" receiving the reflected component and
transforming it into an electrical signal. Analogously, the
distance of the crack circumferentially from the transmitting
transducer and its angular orientation relative to the
circumference are readily calculated from the spatial relationship
of the transmitting and receiving transducers, and the ultrasonic
shear wave travel time.
With reference to FIG. 3, a hard wired circuit is illustrated for
controlling the ultrasonic transducers and for determining the
location of defects. The first array A is oriented to generate
ultrasonic shear waves which propagate circumferentially around a
workpiece 110 and the second array B is oriented to generate shear
waves axially. A position encoder 114 determines the relative
position between the workpiece and the transducer arrays, and a
clock 116 periodically generates clocking pulses. A Schmidt trigger
or other triggering means 122 converts the clock pulses into firing
pulses of the appropriate amplitude and duration for causing one of
the ultrasonic transducers to generate an ultrasonic shear wave. A
multi-plexing means 124 selectively switches the trigger pulses
from the trigger means serially to each individual transducer of
the first and second arrays. Each clocking pulse steps the
multiplexer such that the trigger pulses are switched serially to
each transducer.
An ultrasonic wave travel time measuring means 126 measures the
travel time between transmission of an ultrasonic wave and receipt
of an ultrasonic reflected component. A location determining means
120 determines the location of a defect for display on a display
means 130. In the embodiment of FIG. 3, the location determining
means includes an ultrasonic shear wave velocity determining means
132 which determines the velocity of the shear waves along the
measured object. As illustrated, the shear wave velocity measuring
means measures the travel time over a preselected, known spatial
distance. A multiplying means 134 multiplies the wave travel time
by the shear wave velocity to determine the total distance traveled
by the wave, ie., d.sub.42 +d.sub.46. A transducer identifying
means 136 is operatively connected with each of the transducers in
the first and second arrays to determine which transducer was
triggered and which transducer received the reflected component. A
transducer spatial relationship determining means 138, such as a
look-up table, determines the spatial relationship between the
transmitting and echo receiving transducer.
From the spatial relationship of the transmitting and receiving
transducers and the wave travel distance, a relative location means
140 determines the distance along the transmission axis between the
transmitting transducer and the defect as well as the angle of the
defect surface relative to the transmission axis. From the spatial
relationship of the transmitting and receiving transducers and the
actual wave travel distance, a unique defect location and angle is
dictated. An angle look-up table 142 and a relative location
look-up table 144 are preprogrammed with the relationships between
transducer spatial relationships and wave travel distance.
Alternately, the relative location means may be a processor
preprogrammed for implementing equations (3) and (6) set forth
above, and analogous equations for the other transmitting and
receiving transducer combinations.
A coordinate origin adjustment means 150 defines a unique
coordinate position on the workpiece relative to a preselected
origin point on the work-piece. The origin means 150 includes a
position encoder 114 for determining the axial and circumferential
position of the examined object 110 relative to the first and
second transducer arrays A and B. Specifically, the origin
adjustment means compensates for the relative position of the first
and second arrays and the examined object, and compensates for the
position of the transmitting transducer in the array.
An amplitude detecting means 160 determines the relative amplitude
between the transmitted and received pulses. The display means 130
produces a visual display which indicates the location of each
defect, the relative reflectivity of the defect surface, the
angular orientations of the defect surfaces, and the like.
The invention has been described with reference to the preferred
and alternate embodiments. Obviously, modifications and alterations
will occur to others upon reading and understanding this
specification. It is intended to include all such modifications and
alterations insofar as they come within the scope of the appended
claims or the equivalents thereof.
* * * * *